WebGL bufferSubData is not working when trying to set a point size during a mousemove event -

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i want draw different point sizes during mousemove events using webgl. example, press mouse , draw points size of 1 pixel. select different size , when press mouse , move, can draw points new size.

i discovered strange , appreciate feedback.

  1. i created array of point sizes:

    var pointsizes = new uint8array(2000);

  2. i added attribute shader point sizes:

    attribute float pointsize;

    the main function has: gl_pointsize = pointsize;

  3. if populate array size, works fine long not bind in mousemove event:

    for(var = 0; i<=1999; i++)     {pointsizes[i] = 5.0;}  //draw points of size 5   apointsizebuffer = gl.createbuffer(); gl.bindbuffer(gl.array_buffer, apointsizebuffer); gl.bufferdata(gl.array_buffer, pointsizes, gl.static_draw); apointsize = gl.getattriblocation(program, "pointsize"); gl.vertexattribpointer(apointsize, 1, gl.unsigned_byte, false, 0, 0); gl.enablevertexattribarray(apointsize);

  4. as bind buffer , set buffersubdata in mousemove event, no points shown when move mouse. note: index variable increases mouse move identify position in vertex related pixel. here code in mousemove event:

    gl.bindbuffer(gl.array_buffer, apointsizebuffer); pointsizes[index] = fpointsize;  //this selected size gl.buffersubdata(gl.array_buffer, index, pointsizes[index]);

    it not matter if of these things:

          gl.buffersubdata(gl.array_buffer, index, fpointsize);

    or even:

          gl.buffersubdata(gl.array_buffer, index,1);

thanks again help

gl.buffersubdata expects 3rd argument typearray. pointsizes[index] appears uint8. try use pointsizes.subarray(index, index+1) , see if fixes it.


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